1. Field of the Invention
The present invention relates to a delay device, method and random number generator using the same, and more particularly, to a delay device, method and random number generator capable of generating delayed input signal(s) for random component(s), in order to enhance the randomness.
2. Description of the Prior Art
A random number generator is widely used for cryptography application, to provide an unpredictable or nondeterministic value for the generation of nonce, challenge, or a key of symmetric/asymmetric cipher algorithm. The entropy source of the conventional random number generator has several random components with identical or diverse duplications, and the output of each random component can be combined to output a random result.
Conventional random components can be classified into two types: jitter-based and metastability-based. Both types of the random components can generate random bits. In general, the randomness of the random bits depends on environmental issues such as process, voltage, and temperature. For example, the overlay shifts of the process may influence the randomness. Since the overlay shifts may cause certain regularity on the performance of the random components, the random bits outputted by the random components may deviate from true randomness. Sometimes the regularity may cause the random components to generate the same bits continuously (e.g. a series of 1 or a series of 0), or cause periodicity to occur in the output random bits. As a result, the randomness will be reduced.
In order to achieve higher randomness, the entropy source of the conventional random number generator always utilizes a large quantity of random components and combines the output results of these random components. However, such a large quantity of random components may consume considerable power and large circuit area. In addition, the random components are usually implemented by using the standard logic cells based on the process, of which each of the standard logic cells possesses consistency to some extent, such that the randomness of the combinational results of the homogeneous random components may not be satisfactory. Moreover, trigger signals for the random components are always generated from the same system clock; hence periodicity of the system clock may cause the random components to have similar triggering performance. Therefore, there is a need for improvement of the prior art.